Name as Substituent On a molecule with a higher priority functional group,C=O is oxo-and -CHO is formyl. Aldehyde priority is higher than ketone. COOH CHO 3-methyl-4-oxopentanal 3-formylbenzoic acidName as Substituent On a molecule with a higher priority functional group, C=O is oxo- and -CHO is formyl. Aldehyde priority is higher than ketone. CH 3 C CH CH 3 CH 2 C H O O COOH CHO 3-methyl-4-oxopentanal 3-formylbenzoic acid